GB2138117A - Refrigeration apparatus with adjustable refrigeration capacity - Google Patents

Description

1

SPECIFICATION

Refrigeration apparatus with adjustable refrigeration 65 capacity This invention relatesto a refrigeration apparatus, and more particularly, to a mobile refrigeration apparatusfor usewith land or marine containers. The apparatus is intended for controlling thetemperature of the refrigerated space overa widetemperature range covering both the domain of lowtemperatures below -5'C or -6'C (hereinafter referred to as "ref rigeration domain") and that of higher temperatures above -YC or - 60C (hereinafter referred to as "chilled domain").

In general refrigeration apparatus with a wide range of operating temperatures is used primarilywith containers that are subject, in operation, to a wide range of ambient airtemperature fluctuations. Previously known refrigeration apparatusfor container use is so constructed asto usually operate in two modes,that is, a refrigeration modefor controlling the hold temperature of the container at a lowtemeprature below -5'C or -6'C in the refrigeration domain and a cold storage mode forcontrolling the temperatureto a highertemperature above -50C or -60C in the chilled domain. To this end, the cooling capacity of the container refrigeration equipment is set atthe capacity requirement for the refrigeration mode, that is, at a capacity sufficientto keep the hold temperature, for example, at - 18'C under an ambient airtemperature of380C.

Accordingly in the case of cold storage operation for maintaining the hold temperature within the chilled domain, there arises an excess cooling capacity under low ambient airtemperature conditions, resulting in a problem of being unable to maintain the desired hold temperature.

In orderto solve this problem, it has been suggested to control the hold temperature by installing a hot gas by-pass passage, bridging across the high pressure gas line and low pressure liquid line and introducing hot gas to the evaporator thereth rough.

While the refrigeration equipment of the conven- tional method is also shown in the description and drawings of US Patent 3,692,100, it is constructed, as shown in Fig. 10, so as to install, on the high pressure gas line connecting the discharge side of a compressorA with the inlet side of an air-cooled condensor Cl, a hot gas by-pass passage by-passing said condenser Cl, water-cooled condenser C2, drier R and expansion valve EV, all in-series connected, a solenoid valve SV and a temperature contol valve TVwith a sensor T, on said hot gas by-pass passage. Bythis means it is possible to control the hold temperature within the chilled domain through the temperature control of supply air u nder hot gas by-pass operation.

Thus, in the case of cold storage operation, the solenoid valve SVis open and the temperature control valve TVopened when the supply ai r temperatu re is below the temperature setting, so that hot gas is fed into said low pressu re 1 iquid line D and after being GB 2 138 117 A 1 mixed with liquid refrigerantfed through expansion valve EV, introduced into evaporator E. Thus it is arranged to control the hold temperature within the chilled domain by adjustment of the supply air temperature.

When the hold temperature setting is low or, even though said temperature setting is high, when the ambient airtemperature is higherthan said temperature setting, that is, in the hatched area Mof Fig. 9 of the accompanying drawings, it is possible with the conventional refrigeration apparatus to control the hold airtemperature bythe hot gas by-pass method.

However, when the temperature setting is high and the ambient airtemperature is lower,that is, in the unhatched are a Nof Fig. 9,there arises a problem of not being able to control the hold airtemperature by means of hot gas by-pass because in this area N, the heating effect decreases with the increase of the refrigeration capacity.

Furthermore,the expansion valve EVis generally of thetype of thermostatic expansion valvewherein the opening is controlled by sensing thetemperature of low pressure gas and as stated above, in the case of hold temperature control by means of hot gas by-pass, low pressure gas atthe outlet of evaporator E becomes superheated by by-passed hot gas, the opening of the expansion valve EVwith a feeler bulb attached to low pressure gas line G being increased further. As a result, even when the ambient air temperature becomes lowerthe liquid refrigerant flowthrough said expansion valve EVis increased because of the valve opening that is equal to or larger than that in the case of high ambient airtemeprature.

Therefore, underthis condition, even if a hot gas by-pass means is employed, it is impossible to control the hold temperature becausethe heating effect thereof is overcome bythe cooling effect of liquid refrigerant. Further, with the increase of valve opening of said expansion valve EV, the power in-put of the compressorwill also increase, thereby resulting in waste of energyand failureto meetthe requirements of energy conservation.

It is an object of the present invention to avoid or minimize one or more of the above disadvantages and in particularto control, while controlling the supply air temperature by means of hot gas by-pass, the opening of the expansion valve installed on the liquid line by using the pressure of the by-passed hotgas, thereby reducing the liquid refrigerant flow through said expansion valve and broadening the control range of the hold temperature as widely as possible and atthe sametime reducing the energy inputto the compress- or at low load operation, thereby meeting the requirements of energy conservation.

Thusthe present invention provides a refrigeration apparatus having a compressor, a condenser, an evaporator, a thermostatic expansion valve with an equalizer line which is connected to a low pressure line, connecting the suction side of said compressor with the outlet of said expansion valve and incorporating capacity control meansfor controlling the refrigeration capacityof said refrigeration apparatus,the The drawing(s) originally filed was/were informal and the print here reproduced is taken from a later filed formal copy.

2 GB 2 138 117 A 2 control means comprising a hot gas by-pass passage for introducing hot gas discharge from said compress or, by by-passing said condenser and expansion valve, into said evaporator, a hot gas valve installed in said hot gas by-pass passage for controlling hot gas flow into said evaporator, a control passage con nected to the outlet side of said hot gas valve in said hot gas by-pass passage for introducing, in use ofthe apparatus, a portion of the hot gas flow into said equalizer line so as to control the opening of said 75 expansion valve bythe pressure of hot gas, and a communication shutoff valve means for shutting off, upon closing of said hot gas valve, communication between said hot gas by-pass passage and said equalizerline. 80 Thus according to this invention a refrigeration apparatus has a compressor, a condenser, an evapor atorwith an equalizer line connected to a lowpressure linethat connects compressor suction and expansion valve outlet, a means of controlling the refrigeration 85 capacitythat incorporates (1) a hot gas by-pass passage whereby hot gas discharge from said com- - pressor is introduced to said evaporator by by-passing said condenserand expansion valve, (2) a hot gas valve installed on said hot gas by-pass passage and 90 controlling hot gas to be introduced to said evapor ator, (3) a control passage connected on the secondary side of said hot gas by-pass passage and introducing a portion of hot gas into said equalizer line to control the opening of said expansion valve by hot gas pressure 95 and (4) a communication shut-off valve that shuts off, atthe close of said hot gas valve, the communication between said hot gas by-pass passage and said equalizer line. Bythis means of control, it is possible to reducethe opening of said expansion valve by 100 throttling when hot gas is employed to reduce the refrigeration capacity, thereby reducing the re frigerantflowthrough said expansion valve and in turn reducing the refrigeration capacity and broaden ing the control range of supply airtemperature when 105 the loading is low, thereby contributing to minimiza tion of compressor input.

Thus the present invention not only provides control of refrigeration capacity by hot gas by-pass to the evaporator but also improves the accuracy of the 110 refrigeration capacity control by control ling the open ing of the expansion valve by use of said by-passed hot gas and enables the ref rigeration apparatus to control its refrigeration capacity even at a low loading, for example, when the temperature setting is high or when the ambient air temperatu re is lower than the temperature setting, thereby extending the control range to the unhatched area N of Fig. 9. Thus even at extremely low ambienttemperatu res and attempera ture settings higherthan such ambienttemperatures, refreigeration capacity control is possible, the opera tion range being extendedthat much.

Furthermore, because it is possibleto reduce the opening of said expansion valve during refrigeration capacity control by by-passed hot gasthe refrigerant 125 flow circulated through the refrigeration circuit is reduced,thereby minimizing energywastage.

Preferably, the hot gas valve and the communica tion shut-off valve of the control means are of the solenoid valve type, being electrically actuated and controlled by a controller. The controller incorporates a temperature sensorfor sensing at least one of the return airtemperatureto said evaporator and the supply airtemperature from said evaporator, a setting input unit for input of the desired temperature setting, and a central processing unitthat compares the temperatureof a leastone ofthe return airandsupply airwith thetemperature setting and outputs a control signal forcontrol of said hotgasvalveand communication shut-off valve.

Advantageouslythe hotgasvalveisofthe electromagnetic proportional control valve type wherein the opening iscontrolled in proportion to the voltage applied and said communication shut-off valve comprises either athree-way control valve, an on-off controlled stop valve, or a plurality of said stop valves.

While said hot gas by-pass passage is intended to be installed between the high pressure gas line and low pressure liquid line, it is advisableto make said connection with the low pressure liquid line atthe distributor installed atthe inletside of the evaporator, asthis results in good mixing of liquid and gas refrigerant.

Further preferred features and advantages of the invention will appear from thefol [owing detailed description given bywayof example of some preferred embodiments illustratedwith referencetothe accompanying drawings in which:

Fig. 1 is a refrigerantf luid circuit diagram of a first embodiment of a refrigeration apparatus of the invention; Fig. 2 is an enlarged scale sectional view of a distributorwith a hot gas by-pass passage connection, suitable forthe apparatus of Fig. 1; Fig. 3 is an electrical circuit diagram of the refrigeration apparatus of Fig. 1; Fig. 4 is aflow chart of the operations sequence of the refrigeration apparatus of Figs. 1 to 3; Fig. 5 is an explanatory temperature difference rangediagram; Figs. 6 to 8 are detailed refrigerant fluid circuit diagrams showing principal features of further embodiments; Fig. 9 is a graph showing the relation between supply airtemperature and ambient airtemperature; and Fig. 10 is a refrigerant fluid circuitdiagram fora known embodiment.

Fig. 1 is a typical embodiment of the refrigeration apparatus of this invention, wherein reference numeral I designates a compressor, 2 an air-cooled condenser, 3 a water-cooled condenser, 4 an evaporator, 5 a thermostatic expansion valve having an equalizer line 51 and a feeler bulb 52, and 6 designates refrigerant piping inter-connecting these elements and constituting a refrigeration circuitto cool the hold air by said evaporator4.

Moreover, said refrigeration equipment is also equipped with accessories such as accumulator and receiver combined 7, drier 8, solenoid valvefor pump-down 9, liquid indicator 10 distributor'll, safety device 12 having a high an low pressure combination switch HLPS, an oil pressure protection switch OPS, a water pressure switch WPSand a higher pressure control switch HPSevaporatorfan 13 a GB 2 138 117 A 3 provided on evaporator4, and condenserfan 14 provided on said air-cooled condenser 2.

Furthermore, a means of control is incorporated as stated belowto control the refrigeration capacity of the refrigeration equipment above constituted. Said means of control consists of a hot gas by-pass passage 20, a hot gas valve 21, a control passage 22 and a communication shut-of valve 23. Said hot gas by-pass passage 20 is provided between high pressure gas line 6a, connecting the compressor outlet with the air-cooled condenser inlet, and low pressure liquid line 6b, connecting said expansion valve 5 with said evaporator 4, and introduces the hot gas discharged form said compressor 1 directly into said evaporator 4, by-passing said condensers 2,3, said accumulator and receiver combined 7 and said expansion valve 5. Said hot gas valve 21 is installed on the hot gas by-pass passage 20 and controls the hot gas to be introduced into said evaporator 4. Said control passage 22 is installed on the secondary side of said hot gas valve 21, being connected with the equalizer line 51 of said expansion valve 5 connected to low pressure gas line 6cand controlsthe opening of said expansion valve 5 by introducing a portion of hot gas to said equalizer line 51. Said communication shut-off valve 23 is installed atthe junction point of said control passage 22 and said equalizer line and shuts off the communication between said hot gas bypass passage 20 and equalizer line 51 atthe close of said hot gasvalve2l.

At said hot gas valve 21, a solenoid valve of on-off type may be used but an electro-magnetic proportional control valve is preferably used because it is able to control the opening overthe range of 0%-100% in proportion with the voltage applied, which isto be controlled by a controller 24 as described below.

Moreover, said communication shut-off valve 23 is preferably, as shown in Fig. 1 of thetype of three-way solenoid valve wherein said control passage 22 is connected to one of the two switch-over ports thereof, No. 1 equalizer line 51a of the equalizer line 51 to the other switch-over port and No. 2 equalizer line 51b of the equalizer line 51 to the fixed port, which is to be switched-over between said control passage 22 and No. 1 equalizer line 51a.

Furthermore, the outlet side of said hot gas by-pass passage 20 is to be connected, as stated above, to low pressure liquid line 6b and although its connection point is not specifically limited, it is recommended to use a distributor 11 shown in Fig. 2 and connect said 115 outlet side to this distributor 11. The distributor 11 is so constructed asto have a mixing chamber 11 con the distributor main body 1 lb having a plurality of distribution passages 1 laa nozzle port 11datthe connection side of said low pressure liquid line 6b and 120 a hot gas supply port 11 ethrough which hotgasis introduced into said mixing chamber 11 c.

In this case it is desirable to displace said supply port 11 efrorn the center of said mixing chamber 11 cand introduce hot gas tangentially into said mixing cham- 125 ber 11 c, thus resulting in good mixing of liquid refrigerant passed through said nozzle port 11 dand hotgas.

In the next place, the explanation is given about the controller 24 that controls the supply air temperature130 at a desired temperature by controlling said hot gas valve 21 and communication shut-off valve 23 and the electrical wiring of said refrigeration equipment incorporating said controller 24, based upon Fig. 3.

Shown in Fig. 3 is an electrical wiring diagram of the refrigeration equipment shown in Fig. 1 wherein provided are one compressor-motor MC, two fanmotors ME,, MFI, fortwo fans 13,13 attached to said evaporator 4, threefan-motors MF2, MF2, MF2 for three fans 14,14,14 attached to said air-cooled condenser 2, two defrosting heaters H1, H2 attached to said evaporator 4, four heaters H3- H6 for heating the hold air and two drain port heaters H7, Hs, all of these being connected to power source by selecting either low voltage source plug P, or 200V or 220V or high voltage source plug P2 of 380V-415Vor440V and said controller 24 and controllers for said motors and heaters being connected to power source through transformer Tr.

Further in Fig. 3, CBis a circuit breaker, OCan over-current relay, 2X12X2 auxiliary relays and contacts, 3-88 an on-off switch, contacts with designation code the switch-over contacts by the selection of said PlUgSP1rP2- Said controller 24 consists of an in-put transformer ITr, power source in- put u nit PCB 1, a sensor in-put unit PCB2, an operation in-put and out- put unit PCB3, a central processing unit (hereinafter called as CPU) PCB4, an output display and setting input unit PCB5 and a relay output unit PCB6, wherein relays of said electrical components, that is, a compressor relay 88C, a solenoid relay 20S, of the pump-down solenoid valve, a solenoid relay2OS2 of said communication shut- off valve 23, a heater relay 88H, forsaid defrost heatersH1, H2, a heater relay 88H2 for said hold air heaters H3 - H6 and a fan-motor relay 88Ffor fan-motors MFI are connected, through terminal boa rd PCB7, onto the output end of said relay output unit PCB6, motorized part 20M of said hot gas valve 21 being connected, th rough said terminal board PCB7, to the output end of said operation input and output u nit PCB3.

As shown in Fig. 1, RS is a return sensor placed on the suction side of said evaporator 4to sense the temperature of the return airfrom the hold,that is, the suction air and SSa supply sensor placed on the outlet side of said evaporator 41o sense the temperature of the supply air, each output end being connected to said sensor input unit PCB2. DTis a defrost sensor and OTan over-heat sensor, each being connected to said sensor input unit PCB2.

Besides, 49 is a safety protection device of the compressor consisting of an over-current relay OC and in-series connected high pressure and low pressure combination switch HLPS, said protection device being connected to the input end of said compressor relay 88C. 3D is a manual defrost switch, 30L a reset switch forthe oil pressure protection switch explained in Fig. 1 and 3-30L a lamp switch.

In the hook-up above explained, said return sensor RSand supply sensor SSare so arranged that when the temperature setting SETTselected by said setting input unit PCB5 is lower than -5C for example, said return sensor RS is switched on and when it is higher than VC, said supply sensor SS is switched on. When 4 said return sensor RS is switched on, said compressor relay BBC, fan-motor relay 88Fand said solenoid relay 20S, are energized and said solenoid relay 20S2 deenergized, thus said control passage 22 being closed and the communication between No. 1 and No.

2 equalizer lines opened and operation of ordinary refrigeration cycle run underthe control of suction air temperature.

In the case that supply sensor SS is switched on, a cold storage operation is run, the sequence of which is explained in accordancewith the flow chart shown in Fig. 4.

Atthe start-up, said solenoid relay 20S, being deenergized, said solenoid valve 9 remains closed, with the circuit held in the pump-down state as a result 80 of the pump down operation run after completion of the previous operation.

Underthis condition, when a cold storage operation is selected by said setting input unit PCB5, the supply sensor SS is switched on and comparison is made by CPUPC84 between supply airtemperature SUPTto be sensed by said sensor SS and temperature setting SETT.

When thetemperature difference AT, between said temperature setting SETTand supply airtemperature SUPTeies in the range wherein the condition, A'C (SETT-SUPT) < 2'C applies, that is, range Xof Fig. 5, said solenoid relay 20S, is energized together with compressor relay 88Cand fan-motor relay 88F. And said solenoid relay20S2 is energized,thus communi cating said control passage 22 with No. 2 equalizer line 51b and disconnecting No. 1 equalizer line 51a and the motorized portion 20M of said hot gas valve 21 is applied with a voltage, which opens said hot gas valve 21 in an opening corresponding to the voltage applied At the opening motion of said hot gas valve 21, a portion of hot gas passing through hot gas by-pass passage 20 is introduced, in a flow rate corresponding to said valve opening, into No. 2 equalizer line 51b of said expansion valve 5 and throttles said expansion 105 valve in an opening corresponding to the pressure of said hot gas.

Therefore, the liquid refrigerantflow ratethrough said expansion valve 5 decreases in accordance with the valve opening and hot gas of desired flow rate is introduced into evaporator 4 through said distributor 11. Underthe condition of reduced capacity bythe reduction of the opening of said expansion valve 5, it is possibleto provide heating by hot gas and to control the supply airtemperature by said hot gas with a high accuracy. Moreover, the control of the opening of said hot gas valve 21 is made by comparison of the temperature between temperature setting SETTand supply airtemperature SUPTto be sensed by supply sensor SS. The voltage applied on the motorized portion 20M of said hot gas valve 21 remains constant when both are same and is decreased when supply air temperature SUPTis higher than temperatu re setting SETTand increased when supply air temperatu re SUPTislower.

As a result of hot gas by-pass that controls the valve opening of hot gas valve 21, when said temperature difference AT, remains within the range above stated, the control of supply airtemperatu re is continued by means of this control system. However, when the GB 2 138 117 A 4 temperature difference AT2 between said supply air temperature SUPTand temperature setting SETT comes into the range wherein the condition, (SUPTSETT) > VC applies, that is, Range Y of Fig. 4, solenoid relay2OS2 is deenergized and switches oversaid communication shut-off valve 23 so as to closethe communication between said control passage 22 and No. 2 equalizer line 51b and motorized portion 20Mof hot gas valve is deenergized,thus switching the operation to that of ordinary refrigeration.

By this operation, is said temperature difference AT, is reached, the control is switched overto said hot gas control system and while said temperature difference AT2 is retained, said refrigeration operation is needless to say, continued.

When supply airtemperature SUPTdoes not rise even with hot gas by-pass operation andthetemperature difference AT3 between supply airtemperature SUPTand temperature setting SETTlies in the range wherein the condition, (SETT- SUPT) > 20C applies, that is, Range zof Fig. 5, compressor relay 88C, fan-motor relay 88Fand said solenoid relay 20S, are deenergized to stop said compressor 1 and fans 13,14 and close solenoid valve9. Said solenoid relay 20S2 is also deenergized to switch overthe communication shut-off valve 23,the motorized portion 20Mof hot gas valve 21 being deenergized. In this case, the close of said soleoid valve 9 is made for pump-down procedure and has no relationship with the control of operation. And heater relay 8SH2 is energized to supply currentto hold air heaters H3 - H8.

When said temperature difference AT3 enters, by said current supplyto heaters H3 - H8, into the range wherein the condition, (SETT - SUPT) < 'I'C applies, said heater relay 8BH2 is deenergized to cut the current supply to said heaters H3 - H8, and as shown byArrow Ill, the operation moves to the control system by use of hotgas.

Furthermore,when said temperature difference AT3 lies in the range wherein the condition (SETT- SUPT) > VC applies, heating operation bysaid H3- H8 isto be continued.

During the cold storage operation by switch ing-over to said supply sensor SS, the case that the tempera- ture difference AT4 between said temperature setting SETTand air supply airtemperature SUPTlies in the range wherein the condition, -VC >(SETT - SUPT) > 20C applies,that is, RangeY +Range Z of Fig. 5 is explained.

In this case, the operation is composed of the control system of Range Yof said temperature difference AT2 and that of Range Z of the temperature difference AT3. When said temperature difference AT4 lies in the range wherein (SUPT- SETT)> VC applies, that is, the range of said temperature difference AT2, said solenoid relay 20S1, compressor relay 88Cand fan motor relay 88Fare energized to drive said compressor 1 and fan motors 13,14 and an ordinary refrigeration operation is run.

As a result of said refrigeration, when said temperature difference AT4 enters into the range wherein (SUPT-SETT) <1'Capplies,the operation shifts, as shown byArrow 11, to the operation of the control system by use of hot gas. While said temperature difference AT4 lies in the range wherein (SUPT -SETT) i 1 Z GB 2 138 117 A 5 > 10C, said refrigeration operation is continued.

Moreover,when saidtemperature difference AT4 lies in the range wherein (SETT- SUPT) > 2'C applies, that is,the range of saidtemperature difference AT3 only said heater relay 8BH2 is energized to run heating 70 operation by said hold air heaters H3 - H8.

As a result of this heating operation, when said temperature difference AT4 becomes less than VC, said heater relay 8BH2 is deenergized to disconnect said hold air heaters H3 - H8 and the operation shifts, as 75 shown by Arrow 11 [,to the operation of the control system by use of hot gas, and when the temperature difference AT4 is more than 'I'C, the heating operation is continued with the same control as explained in RangeZ As explained above, when supply airtemperature SUPTenters into the range appropriateto temperature setting SET7 that is, said RangeX, the control by use of hot gas is made. This control being not only to by-pass hot gas but also to introduce a portion of hot gas, in proportion with the by-pass flow rate, into the equalizing line of said expansion valve 5, thus adjusting the opening of said expansion valve 5, it is possible to provide heating by hot gas while holding the refrigeration capacity at a reduced capacity and control the hold air at a desired temperature regardless of the ambient airtemperature and temperature setting and extend the range of control to the domain otherthan the hatched domain of Fig. 8 and, in addition, reduce the compressor input.

In the above explained example of embodiment, said supply sensor SS is used forthe opening control of said hot gas valve 21, sensing the supply air temperature and comparing with the temperature setting, butthe return sensor RS may be used forthis purpose, sensing the suction airtemperature. Pressure sensorsensing the lowside pressure or high side pressure is also applicable.

Otherwise, it is also applicableto sense the temper- ature difference between suction air and supply air and control the opening of said hot gas valve in proportion with thistemperature difference.

Furthermore, while a three-way solenoid valve is used forsaid communication shut-off valve 23, it is possibleto use, as in Fig. 6, two solenoid valves 23A, 238, one in said control passage 22 and the other in the - equalizer line connecting said control passage 22 and low pressure gas line 6C.

Moreover, as shown in Fig. 7, one solenoid valve 23Cmay be used, being installed on said control passage 22.

Furthermore, as shown in Fig. 8, No. 1 solenoid valve 15 may be installed on the high pressure liquid line 6dconnecting said water-cooled condenser 3 with said thermostatic expansion valve 5, or more particularly receiver 7 with thermostatic expansion valve 5, togetherwith a parallel circuit consisting of No. 2 solenoid valve 16 and in-series connected throttling device 17 such as capillarytube.

Because it is possible in this case to control the flow rate of liquidrefrigerant by closing No. 1 solenoid valveandopening No. 2 solenoid valve and feeding through saidthrottling device, a fine control of operation is possible by joint use of hot gas by-pass control.

While, a three-way solenoid valve is used in Fig. 8 as in Fig. 1 for said communication shut-off valve, it is also possible, as shown in Fig. 6 and Fig. 7 to usetwo solenoid valves 23A, 23B or a solenoid valve 23C instead of said three-way solenoid valve. No. 1 solenoid valve 15 and No. 2 solenoid valve 16 are also applicable to the pump-down operation.

While air-cooled condensor 2 and water-cooled condenser 3 are jointly used as condensers, single condenser 2 or3 is also applicable. While said equalizer line 51 is connected to the low pressure gas line 6c, the con nection point thereof is not limited to said low pressu re gas line 6c, so long as it lies in the low pressure range between the suction side of said compressor 1 and said expansion valve 5. - Because this invention provides, on the outlet side of said hot gas valve 21 of said hot gas by-pass passage 20, a control passage that connects with the equalizer line 51 of the expansion valve 5 and controls the opening of said expansion valve 5, it is possible to reducethe refrigerant flow through said expansion valve5,thus improving the accuracyof control by use of hotgasand provide the control of supplyair temperature even under a low heat loading such as a high temperature setting or an ambient airtemperature lowerthan the temperature setting. In other words, it is possible, as shown in Fig. 9, to extend the control range of the airtemperature by use of hot gas in the chilled domain.

Moreover, becausethe opening of said expansion valve can be controlled during the hot gas by-pass operation, the refrigerant circulation flow rate is reduced, which results in the reduction of compressor in-put and elimination of wasted energy.

Claims (10)

1. A refrigeration apparatus having a compressor, a condenser, an evaporator, a thermostatic expansion valve with an equalizer line which is connected to a low pressure line, connecting the suction side of said compressorwith the outlet of said expansion valve and incorporating a capacity control meansfor controlling the refrigeration capacity of said refrigeration apparatus, the control means comprising a hot gas by-pass passage for introducing hot gas dis- charge from said compressor, by by-passing said condenser and expansion valve, into said evaporator, a hot gas valve installed in said hot gas by- pass passagefor controlling hot gas flow into said evaporator, a control passage connected.to the outlet side of said hot gas valve in said hot gas by-pass passage for introducing, in use of the apparatus, a portion of the hot gas flow into said equalizer line so as to control the opening of said expansion valve bythe pressure of hot gas, and a communication shut-off valve means shutting off, upon closing of said hot gas vlave, communication between said hot gas by-pass passage and said equalizer line.

2. A refrigerations apparatus according to claim 1, wherein said control means includes a controller that controls said hot gas valve and communication shut-off valve means, said controller being equipped with sensors to sense at least one of the return air temperature orthe supply airtemperature from said evaporator, a setting input means for input of a desired temperature setting and a central processing 6 GB 2 138 117 A 6 unit arranged for comparing the desired temperature setting with atleastone of the return airtemperature and the supply airtemperature, said hotgasvalve and communication shut-off valve means being of electrically operated type and being so wired as to be on-off controlled bythe control signal outputfrom said controller.

3. A refrigeration apparatus according to claim 2, wherein are provided electrical heating means said central processing unit of said controller being arranged for controlling said compressorsand heating means and control means forstopping said compressorand operating said heating means, when thetemperature difference between the desired temperature setting and eitherthe return airtemperature orthe supply airtemperature exceeds the previously set value.

4. A refrigeration apparatus according to anyone of Claims 1 to 3wherein said hot gasvalve is an electromagnetic proportional control valve formed and arranged forvarying its opening in proportion to an applied voltage.

5. A refrigeration equipment according to anyone of claims 1 to 4, wherein said communication shut-off valve means is a three-way solenoid valve and is disposed atthejunction of said control passage and equalizer line.

6. A refrigeration apparatus according to anyone of claims 1 to 4, wherein said communication shut-off valve means is an on-off solenoid valve and is disposed in said control passage.

7. A refrigeration apparatus according to anyone of claims 1 to 4, wherein said communication shut-off valve means comprises two on-off solenoid valves, one of them being disposed in said control passage and the other in said equalizer line.

8. A refrigeration apparatus according to anyone of claims 1 to 7 wherein said evaporator is provided, at its inlet side, with a distributorto which said hot gas by-pass line is connected.

9. A refrigeration apparatus according to anyone of claims 1 to 8, wherein are provided a No. 1 solenoid valve in the high pressure liquid line connecting said condensorto said thermostatic expansion valve for opening or closing said high pressure liquid line and a control meansfor controlling liquid refrigerant flow, at the close of said No. 1 solenoid valve,through said high pressure liquid line to said thermostatic expansion valve, said control means comprising of a by-pass passage by-passing said No. 1 solenoid valve and having a No. 2 solenoid valve and a throttling means in said by-pass passage.

10. A refrigeration apparatus substantially as described hereinbefore with particular referenceto Figs.

lto5and9,orFigslto5and9asmodifiedin accordance with any of Figs. 6to 8.

Printed in the United Kingdom for Her Majesty's Stationery Office, 8818935, 10184, 18996. Published at the Patent Office, 25 Southampton Buildings, London WC2A IlAY, from which copies may be obtained.

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